Tea

All true tea — green, black, white, oolong — comes from a single plant, Camellia sinensis. What differs is processing: green tea leaves are steamed or pan-fired to halt oxidation, black tea is fully oxidized, oolong sits in between, and white tea is minimally processed young leaves. Herbal "teas" (chamomile, rooibos, peppermint) are not tea botanically and don't share the same caffeine or polyphenol profile.

Caffeine and tannins

A cup of brewed tea has roughly 25-50mg of caffeine — about a third to half of drip coffee. Some people who don't tolerate coffee tolerate tea well; others find even tea disrupts sleep if consumed after early afternoon. Tea is also rich in tannins, which bind non-heme iron in the gut. Drinking tea with meals can reduce iron absorption substantially — for someone correcting iron deficiency, the practical advice is to drink tea between meals rather than with them.

Polyphenols and cardiovascular evidence

Tea is one of the densest dietary sources of polyphenols, particularly catechins (notably EGCG in green tea) and theaflavins (in black tea). Large cohort studies, especially from Asia, consistently link regular tea consumption with modestly lower cardiovascular mortality and stroke risk. The magnitude is small but consistent across populations. The advantage holds for both green and black tea; matcha (powdered green tea) delivers more polyphenols per cup because you consume the whole leaf, not an infusion.

Decaffeinated tea retains most of its polyphenols. Bottled and pre-sweetened iced teas can carry as much sugar as soda and lose much of the health appeal — the benefit is for brewed, unsweetened tea.